Limits
Are there any limits on the number of rows I can merge?
This article details the limits associated with the free version of Mail Merge add-on and the limits imposed by Google on Gmail and Google Docs usage.
Mail Merge Limits
*Subject to Google-imposed limits (see below).
Google limits: Emails
If you send hundreds of emails at once, Gmail may send you an error; this is Gmail's way of trying to discourage spamming.
You should also be aware of Gmail Sending Limits.
Therefore, the following workarounds are suggested:
You can track merged rows so you know which emails have been sent before the error occurs; this way, on the next merge you can continue sending emails where you left off.
From Google Docs only:
You can schedule emails so that you spread them out over time, rather than sending them all at once.
You can send emails over SMTP using third-party SMTP providers (such as SendGrid), using your own SMTP server or using other email accounts from (e.g., Yahoo!, Microsoft). You can also send emails over Gmail's SMTP; this would give you an additional 500 emails per day.
Google limits: Letters
When you merge more than 100 pages into a single document, you may receive errors as Google Docs is not designed to handle huge content. So we suggest you merge in batches.